1. Field of the Invention
The present invention relates to a data processor which is constituted a manner capable of operating a bit field having an arbitrary length.
2. Description of the Prior Art
The conventional data processors such as microprocessors realize operation of a bit field having an arbitrary length by repeating execution of an instruction of performing operation on a bit field of a fixed length, or in the case of not having such instruction, by combining an instruction of performing operation on a byte basis with an instruction of performing operation on a bit basis.
In the conventional data processors, in the case where a read-out area of a bit string and a write-in area thereof are overlapped each other for instructions of performing read-out and write-in of the bit string, for example an instruction for moving bit-string data in a memory, bit data read in the second half might be broken in writing the bit data in the first half.
Also, in the conventional data processors, a problem exists that in the case where the length of the bit string is arbitrary, the execution time of an instruction of operating the bit string becomes long in proportion to the length of the bit string, resulting in a break of reception of external interrupt up to the end of execution of the instruction.